Although millions of individuals are exposed to solvent mixtures at work, home and through the air, water, and food contamination, relatively few human studies have addressed the reproductive and genetic consequences of exposure. This study addresses these concerns and represents an optimum design as it is a prospective cohort study with a repeated measures design. Biological samples are collected pre- and post-exposure over three periods separated by fifteen week intervals. The study hypothesis is that duration and intensity of exposure to solvents at levels below the threshold limit values as measured with industrial hygiene sampling data and levels as measured in breath samples will be associated with an increase in adverse mutagenic and spermatogenic alterations. Trends over time will be noted between the baseline (pre-exposure and the two post-exposure biological assays. The specific aims of the study are to 1) test a battery of reproductive and mutagenic assays as early indicators of solvent exposures and 2) to determine the correlation and predictive ability between external exposure measures and internal dose measures and to compare each of these biologic effect markers. The mixed solvent exposure includes 1,1,1- trichloro-ethane, methyl ethyl ketone, xylene and toluene. Twenty-five exposed and 5 control subjects will be followed for a period of one year. Pre exposure mutagen assays and semen analysis are obtained as a baseline measure and then repeated post exposures at two intervals. Breath samples are collected at end of shift on the same day as the other biological samples. In addition, a total of eighteen industrial hygiene measurements divided between sample intervals are collected on each individual to obtain a composite index of a worker's cumulative exposure as well as exposure during each fifteen week period. This study represents an unique opportunity in that a Memorandum of Understanding with the United States Air Force is already in place in support of the study and has the approval of the Air Force Surgeon General's Office. In addition, a pilot study has been completed. The study is being conducted at a military installation, Hill Air Force Base with the voluntary cooperation of military and civilian employees and the full support of the union.